PNEUMATIC TOOLS. 141 PNEUMONIA. tion and in actual use on the accompanying plate. Pneumatic drills are made in a large number of sizes from light drills suitable for small holes up to machines of two or three horse-power. They work with from 00 pounds to 80 pounds air pressure. For performing different kinds of work, assuming the size to be ample, the only change necessarj' is the substi- tution of the proper tool (drill, auger, saw-bit, reamer, etc.) in the tool-holder. A description of the motor construction of several well-known tools will give a fair idea of this mechanism. In the Little Giant drill the motor consists of four single-acting cylinders arranged in pairs and coupled to opposite ends of a crank shaft. The crank shaft carries pinions which gear with spur wheels on the tool shaft. The entire mechanism is inclosed in a shell shaped like the section of a circular cylinder. The Whitelaw drill has two double-acting oscillating cylinders geared to a crank shaft which carries a single pinion gear- ing with a spur wheel on the tool shaft. In the Boyer piston drill the motor is in the form of a three-cylinder single-acting oscillating engine, the cylinders being carried in a rotary frame, which, since the cylinder pistons are coupled to a fixed crank, rotates and by means of suitable gears causes the tool shaft to rotate. The motor mechanism is all inclosed in a cylindrical casing. Air is piped to these rotary tools by flexible hose exactly as in the case of percussion tools. The use of pneumatic tools has been most highly developed in the United States, but it is extending rapidly in European countries. Their particular field of usefulness is in performing work formerly performed by hand, because of the inability of transporting the ordinary heavy shop tools to the work. For example, in riveting the connections of metal bridges during erection in the field the work has to l)e done on stagings and scafi'oldings high in the air. These positions are inaccessible to heavy sliop riveting machines, and imtil the advent of the pneumatic tool such work was of necessity performed liy hand : the portable pneumatic riveter can be used in almost any place where hand riveting is possible with a gain in all things in which machine work sur- passes hand work. PNEUMOGASTKIC (nu'md-gas'trik) NERVE (from Gk. ttvciJ/miiv, piictinion, lung + yaa-T^p. (/aster, stomach ) , or Par Vagum. A nerve which derives the first of its names from its sup- plying the lungs and stomach with nervous fila- ments, and the second from the wandering course which it pursues. It emerges from the medulla oblongata by eight or ten filaments, which unite and form a flat cord that escapes from the cavity of the cranium (in association with the glosso- pharyngeal and spinal accessory nerves) by the jugular foramen. In this foramen it forms a well-marked ganglionic swelling, while an- other is observed immediately after its exit from the skull. The nerve runs straight down the neck between and in the same sheath as the in- ternal jugular vein and the carotid artery. Be- low the root of the neck its course is dilTerent on the two sides; the right nerve, running along the back of the oesophagus, is distributed to the pos- terior surface of the stomach, and finally merges into the solar plexus, while the left nerve runs along the front of the npsophagus to the stomach, sending branches chiefly over its anterior surface. From anatomical considerations, based on the distribution of this nerve, and from the results of experiments (ju animals, it may be concluded that this is a mixed nerve, containing filaments both of sensation and motion. The pulmonary branches exercise a most important influence upon the respiratory acts, for when the pneumo- gastrics on both sides have been divided aljove the giving off of the pulmonary branches, the mast severe dysijuiea comes on, the number of respira- tions is much diminished, and the animal breathes as if it were asthmatic; after a short time the lungs become congested and finally con- solidated, while the bronchial tubes are' filled with a frothy serous fluid ; and if the cut ends of the nerves are kept apart, the animal never sur- vives above three days. The gastric branches in- fluence the movements of the stomach, while their destruction does not materially affect the secretion of the gastric juice of further digestive reac- tions. Loss of voice and difficulty of breathing have been fre(|uentl.y traced to the pressure of an aneurism or other tumor on the recurrent or in- ferior laryngeal. The s.vmpathy which exists be- tween the digestive and the respiratory and circu- lating organs is explained b.y the anatomical re- lations of this nerve. For example, both asthma and palpitation of the heart are often to be traced to some deranged state of digestion. Vom- iting may be excited by irritation of the central or the distal extremities of the nerve. In dis- ease of the brain the vomiting, which is often an early .symptom, is caused by irritation of the central extremity; while, on the other hand, by introducing emetic substances into the stomach the vomiting is produced by the irritation of the peripheral (or distal) filaments. PNEUMONIA, nu-mC.'ni-a (Xco-Lat., from Gk. TTfevfiofla, disease of the lungs, from Trvevfiav, pnenmOn, lung, from trveiv, pnein, to breathe). An inflammation of the substance of the lung. There are three well-defined forms: Acute lobar pneumonia, broncho-pneumonia, and chronic in- terstitial pneumonia. Acute ])neumonia is called lohar because it in- volves usually an entire lobe or successive lobes of the lung: croupous from the character of the exudation into the air cells or alveoli. The dis- ease is due to a specific germ, the Fneumoioccus or Diplococcus pneumoniw, although streptococci and staphylococci are always found with it. It is infectious and in a measure contagious, and sometimes occurs epideniicall.v in institutions and houses. It is apt to attack persons in a de- pressed physical or mental condition: it is more prevalent in the spring and autuiiui tlian at other times, and is a disease of adults up to middle age. I'niike most specific fevers, one attack does not confer inununity, but rather predisposes to others. Pneumonia begins with a chill, high fever, and a severe pain in the side, attributable to the accompanying pleurisy. As the nialad.y progresses, there is a cough, with a viscid, air- less, rustv sputum, later becoming vellow. Respi- rations are rapid and shallow. 40 or 50 to the min- ute: the piilse is also rapid, the cheeks flushed, and the general prostration extreme. There are in addition headache, sleeplessness, and sometimes delirium. These svmptoius continue with more (ir less severity until the crisis occurs, from the fifth to the eleventh day, when the temperature falls quite suddenly, almost to normal, and rapid improvement sets in. In a few cases a crisis does not occur, but the temperature declines gradu-
